First Report of Chickpea chlorotic stunt virus Infecting Legume Crops in Tunisia.

During a survey of legume crops in the northeast and northwest regions of Tunisia in April 2010, plants showing yellowing, reddening, and stunting symptoms were observed. A total of 281 symptomatic samples were collected: 142 plants from 10 chickpea (Cicer arietinum L.) fields, 84 plants from six faba bean (Vicia faba L.) fields, and 55 plants from six pea (Pisum sativum L.) fields. All samples were tested by the tissue-blot immunoassay procedure with the following monoclonal antibodies (MAbs): a broad-spectrum legume-luteovirus MAb (5G4), Faba bean necrotic yellows virus (FBNYV; genus Nanovirus, family Nanovirudae) (3-2E9; provided by J. Vetten, BBA, Braunschweig, Germany), Beet western yellows virus (BWYV; genus Polerovirus, family Luteoviridae) (A5977; Agdia, Elkhart, IN), Bean leafroll virus (BLRV; genus Luteovirus, family Luteoviridae) (4B10), Soybean dwarf virus (SbDV; genus Luteovirus, family Luteoviridae) (ATCC PVAS-650; American Type Culture Collection ATCC, Rockville, MD,), and a mixture of three MAbs (5-2B8, -3D5, and -5B8) to a Syrian isolate of Chickpea chlorotic stunt virus (CpCSV) (1). Serological tests showed that CpCSV was detected in 121 samples (43.06%) (62 chickpea, 57 faba bean, and 2 pea), followed by FBNYV (detected in three faba bean and three pea), BWYV (detected in three chickpea and one faba bean), and BLRV (detected in one pea sample). FBNYV, BLRV, and BWYV have been previously detected in faba bean and chickpea in Tunisia (4), but to our knowledge, this is the first report of CpCSV affecting legumes in Tunisia, which was found in seven chickpea, seven faba bean, and two pea fields. CpCSV has been reported to naturally infect legume crops such as chickpea, lentil, field pea, and faba bean as well as some leguminous weeds and a few wild non-legume plants species in many countries in West Asia and North Africa and causes economic losses on chickpea in Eritrea, Ethiopia, and Syria (1-3). Serological results of CpCSV was confirmed in four (two pea, one faba bean, and one chickpea) samples by reverse transcription (RT)-PCR using CpCSV specific primers (F:5'-TAGGCGTACTGTTCAGCGGG-3' and R:5'-TCCTTTGTCCATTCGAGGTGA-3') (3), which produced an amplicon of expected size (413 bp). No amplification was observed from healthy plant extracts. Sequence analysis revealed that the four Tunisian isolates (TuV 258-201 collected from faba bean [GenBank Accession No. HQ199310], TuC 215-201 collected from chickpea [HQ199307], and TuP 163-201 [HQ199308] and TuP 166-201 collected from pea [HQ199309]) were most similar to each other with a high sequence identity (99%) and clustered with isolates of CpCSV from Syria (GenBank Accession No. EU541270), Egypt (EU541269), and Morocco (EU541267), to which they were most closely related (98%). The Tunisian isolates also showed high sequence identity (96%) in the coat protein region with Ethiopian (GenBank Accession No. EU541257) and Sudanese (EU541263) isolates. However, all isolates are distinct from BWYV, BLRV, and SbDV (less than 70% sequence identity). Since CpCSV is transmitted by aphids only, additional studies are needed to identify the host range of the virus and the efficient aphid vectors to better understand the epidemiology of this virus under Tunisian conditions References: (1) A. D. Abraham et al. Arch.Virol. 154:791; 2009. (2) N. Y. Asaad et al. J. Phytopathol. 157:756, 2009. (3) S. G. Kumari et al. Phytopathol. Mediterr. 47:42, 2008. (4) A. Najar et al. Phytopathol. Mediterr. 39:423, 2000.